A multi-signature transaction is a bitcoin transaction that needs more than one key to verify. This kind of transaction needs at least m of the private keys corresponding to given n regular addresses have to sign a transaction to handle the transaction. At present, a Bitcoin protocol limits the number of N and M at 15. Generally, this is an M-of-N transaction.
Bitcoin transaction: Multi signature transaction
This kind of transaction is very useful for businesses that need to sign two specific transactions or even a co-account, which is the 1-of-2 or 2-of-2 format regularly used.
If a 2-of-3 multi-signature transaction is created, any combination between 2 of this 3 signature could be used to spend the fund.
Following are the codes for locking and unlocking the keys.
<ScriptPubKey> = 2 <Public Key A> <Public Key B> <Public Key C> 3 OP_CHECKMULTISIG
<ScriptSig> = <Signature 1> <Signature 2> or any permutation of Sig 1,2,3.
If everything is correct, then that transaction will be authorized and use widely in the Bitcoin network